“Screen time is associated with being overweight and obese which is associated with high cholesterol and high blood pressure,” said pediatric cardiologist Dr. Stephen Daniels, a spokesman for the American Heart Association. “Once those risk factors, such as obesity, are in play in childhood, they tend to continue into adulthood.”

Dr. David Hill, chairman of the Council on Communication and Media for the American Academy of Pediatrics, agreed: “Heart health starts during childhood, so I think it’s very appropriate that the American Heart Association looks at every issue that can contribute to heart disease.”

A panel of American Heart Association experts reviewed 20 years of science on the relationship between cardiovascular disease, stroke and self-reported screen time by children and teens. They found that while TV viewing is down, the use of mobile screens is up, resulting in an overall net increase.

Today, kids age 8 to 18 are estimated to spend more than seven a hours a day on smartphones, tablets, video games and other screen-based recreational devices, including television.

While time spent being a sedentary TV couch potato might be down, the use of other types of more portable screens doesn’t seem to be increasing activity among youth, the expert panel said.

“Passive viewing is still children’s number one activity,” Hill said. “Whether it’s a video game, or laptop or desktop computer, children are still sitting.”

Since sedentary behavior is linked to obesity risk, and obesity is linked to heart disease, it doesn’t take a detective to figure out the connection.

“There are strong data that relate childhood TV time to obesity in children,” said Hill, adding that it appears to be related to advertising of unhealthy foods and the likelihood that a child will snack while watching television.

“There are real concerns that screens influence eating behaviors, possibly because children ‘tune out’ and don’t notice when they are full when eating in front of a screen,” Tracie Barnett, a researcher at the INRS-Institut Armand Frappier and Sainte-Justine University Hospital Research Center in Montreal, said in a statement.

“There is also evidence that screens are disrupting sleep quality, which can also increase the risk of obesity,” said Barnett, who ledthe American Heart Association writing group.

“Ideally, screen-based devices should not be in bedrooms,” Barnett added, “because some studies have found that having screen-based devices in the bedroom can affect sleep.”

So far, Hill added, research doesn’t show a connection between obesity and social media or gaming, perhaps because it is harder to snack while gaming. But research is having a tough time keeping up with technological advances, said Hill, and long-term research is needed.

The American Heart Association expert panel agreed, adding that little is known about the effects of long-term screen use on children’s health. Parents also need research-based advice, said the panel, on how to break the siren call of screens and improve childhood physical activity.

Current ideas to help parents include getting the whole family active, scheduling a physical activity each day, removing TV and mobile screen devices from the bedroom, and planning TV viewing in advance.